Motion Modeling And Gliding Control Research Of Underwater Gliders

An underwater glider is a novel type of autonomous underwater vehicle withoutexternal propulsion system that glides by controlling adjustable net buoyancy andadjusts attitude by redistributing internal mass to control the location of the centre ofgravity of the vehicle. It has many advantages, such as gliding with high efficiency,wide cruise range，less power consumption, low noise, no pollution etc., which makeit an important platform for marine environment observation and ocean resourceexploration.In this paper, general design of the system, modeling of motion, analysis ofvertical plane gliding motion have been carried out based on self-developed acousticunderwater glider system. Then the transfer function identiifcation and adaptiveFuzzy PID based controller for adjusting the pitch attitude and depth of underwaterglider are designed and analyzed. Finally，a large number of experiments researchhave been executed based on above theoretical analysis and simulation. The maincontributions are summarized as follows:L The overall structure and layout of the underwater glider is designed andanalyzed using a combination of integrated and modular approach. Strength andstability check is carried out on the main cabin pressure hull and net buoyancy changedue to a combination of changes in sea temperature and salinity and the deformationof the body under pressure is analyzed. On the basis of test data, glider powerconsumption for each module is estimated. From the perspective of structure andenergy, a good hardware platform research is built for underwater glider research.2.Under the rigid body assumption for overall movement and multi-body rigidassumption for inside mass movement, kinematics modeling, dynamic modeling andforce analysis for underwater glider are carried out by using vector matrix method,and simultaneous matrix equations are turned into scalar form. Accordingly,simpliifed equations of vertical gliding highlight the relationship between themovement state of controllable mass and gliding attitude of underwater glider.3.Cross-validation reliability analysis based gray box system identificationmethod is used to get vertical movement transfer function on controlling pitch attitudebased on the simplified vertical model and test data in Matlab System IdentificationToolbox. The transfer function model has simplified and amended the theoreticalmodel, which laid the foundation for the study of underwater glider attitude control. 4.On the basis of the identified transfer function, gliding attitude controller isdesigned by using adaptive fuzzy PID algorithm. The simulation results in Matlab/Simulink show that the fuzzy PID controller possesses good control effect in theaspect of dynamic performance, immunity capacity and ability to adapt to differentcontrol objectives, which plays an important guiding role for gliding attitude andgliding depth control actually.5.Finally, a large number of experiments of the glider motion are introduced inthis paper. The design principle of posture adjustment system and buoyancy adjustingmechanism for the underwater glider is verified feasible. Plentiful proifle teststhousand island lake and northern south China sea futher confirms the rationality ofthe parts design and control scheme of the underwater glider.